The present invention relates to a process for producing apertured nonwoven fabric.
Conventional techniques for producing apertured nonwoven fabric include the following:
(1) There has already been proposed a process in which fibrous web is placed on support meshes, and then high velocity water streams are jetted thereonto from above to distribute fibers aside and simultaneously to randomly entangle fibers with each other. At the same time, drainage is effected under suction from below said meshes. This process is disclosed, for example, in U.S. Pat. No. 3,485,706. According to this process of well known art, nackles of said meshes are utilized to form apertures in the fibrous web. However, the water streams jetted thereonto pass through said support meshes, so that it is impossible to use sufficiently the energy provided by the water streams for treatment of fiber entanglement. Certainly it is possible to form apertures in the fibrous web, but the efficiency of fiber entanglement is too low to achieve the desired strength of fiber entanglement. Furthermore, said nackles do not have a height sufficient to achieve the fiber distributing effect. As a consequence the apertures formed in the finished nonwoven fabric are unclearly contoured due to fibers remaining inside the apertures.
(2) There has already been well known a process in which the fibrous web is placed on the support meshes and a patterning plate having a plurality of holes corresponding to a pattern in which apertures are to be formed in the fibrous web is placed on the fibrous web, and then high velocity water streams are jetted from above onto the patterning plate to achieve the fiber distributing effect as well as fiber entangling treatment and simultaneously suction-drainage is effected from below said support meshes. This process is disclosed, for example, in U.S. Pat. Nos. 3,240,657 and 2,862,251. According to this process, the fibers lying below the zones of the patterning plate in which said holes are not present are free from influence of the water streams. The fibers lying below the respective holes of the patterning plate also can not obtain the desired strength of fiber entanglement, since, as in said process (1), the water streams pass through said support meshes and it is impossible to utilize sufficiently their energy for fiber entangling treatment. Moreover, the apertures formed in the finished nonwoven fabric are unclearly contoured due to fibers remaining therein.
(3) There has also already been proposed a process in which the fibrous web is placed on a patterning plate having the plurality of holes corresponding to a pattern in which apertures are to be formed in the fibrous web, and then high velocity water streams are jetted thereonto from above to achieve a fiber distributing effect as well as fiber entangling treatment and simultaneously suction-drainage is effected from below the patterning plate. This process is disclosed, for example, in Japanese Laid-Open Patent Aplication No. 52-59774. According to this process, the patterning plate includes planar zones having no holes and contributing to fiber entanglement. However, the apertures in the fibrous web are formed the that the fibers lying on the zones of the patterning plate in which said holes are not present are displaced under the action of the water streams into said holes in which no fiber entanglement is promoted. As a consequence, efficiency and strength of fiber entanglement are not satisfactory and the apertures formed in the finished nonwoven fabric are unclearly contured due to fibers remaining therein.
Furthermore, these three processes of the prior art require a high flow rate as well as a high jetting pressure of the water streams in order to obtain nonwoven fabric having the desired strength and relatively clear apertures. Such requirements disadvantageously increase a production cost.
An object of the present invention is to provide a process for producing apertured nonwoven fabric having clearly contoured apertures by distributing aside fibers lying on a plurality of projections regularly carried on support means towards surface portions defined between said projections.
Another object of the present invention is to provide a process for producing apertured nonwoven fabric having an excellent fiber rearrangement and the desired tensile strength by causing fiber entanglement at surface zones on which the water streams rebound and twice contribute to fiber entanglement, while effective drainage is achieved through a plurality of drainage holes regularly carried on said support means so that the efficiency of fiber entanglement may be improved at a low jetting pressure and a small flow rate of the water streams.
A further object of the present invention is to provide a process for producing apertured nonwoven fabric which can be carried out with an apparatus of compact construction by arranging the desired number of nozzle means around a cylindrical body of a desired diameter as a preferred embodiment of the support means.
Still other objects and advantages of the present invention will be apparent from the following description of preferred embodiments in conjunction with the accompanying drawings.